(1) Field of the Invention
This invention relates to optical mirrors and more particularly to the fabrication of a high quality mirror from a metal matrix composite (MMC) material.
(2) Background of the Invention
The use of mirrors in high precision optical systems has been known for a long time. Critical to the successful application of these mirrors are material properties such as dimensional stability, low weight, high thermal conductivity, high specific heat, high stiffness, suitable coefficient of thermal expansion, etc. Different applications require various combinations of these properties. For example, many aerospace applications require low weight, high stiffness and high dimensional stability. Beryllium is particularly attractive in this regard. After trying different possible choices beryllium has been used for fabricating such mirrors. They have been fabricated by consolidating beryllium powder by vacuum hot pressing (VHP) into a block which is then machined into the desired shape of a mirror. However, beryllium is a very expensive metal and has limited sources of availability. Furthermore, beryllium is toxic and has very limited near-net-shaping (cast or forged) capability. A high precision beryllium mirror is therefore machined out of a beryllium block, thus wasting most of the beryllium by converting it into beryllium chips. Besides, beryllium is toxic and requires a special machine shop to meet rigid Occupational Safety and Health Administration (OSHA) requirements for safety which adds to its expense. It is thus desirable to fabricate precision optical mirrors out of a material which is nontoxic and cheaper than the beryllium metal.